This invention relates to an endoscope of the type in which a channel tube for inserting a body-cavity treating instrument such as a catheter therein is disposed in a sheath and the base end of the tube extends through the rear end wall of a control section housing, of which the front end is attached to the sheath.
As an endoscope having the above-mentioned channel tube a laparoscope etc. can be listed. As such body-cavity treating instrument use is often made of a generally straight, unyielding one. It is desirable from the viewpoint of operation that a channel for inserting the instrument therein be straight. A channel tube is formed such that it extends straight along the length of the sheath from a control section housing where a manual operation is effected. The base end portion of the channel tube extends through the rear end wall of the control section housing to provide an instrument inserting hole. In the endoscope of this type an optical fiber bundle is disposed in the sheath, but there is no ample room for an eyepiece section to be provided at rear end of the control section housing, the eyepiece section and optical fiber bundle constituting part of an observation system. For this reason, the eyepiece section is provided at the side section of the housing and, for example, a prism is provided to permit an optical axis of the observation system to be bent. In this method, however, a higher degree of skill is required from the standpoint of assembly in adjusting the position of a prism and, moreover, the misalignment of the optical system tends to occur from the structural viewpoint, failing to obtain a proper optical performance. From this viewpoint, a specific manufacturing technique is required in the assembly of endoscopes and it is also difficult to mass-produce. Thus, production problems are encountered in the prior art.